Transformation-stable composition comprising viscous polyamide, production thereof and use of same

ABSTRACT

The use of at least one catalyst, at least one copper heat stabiliser and at least one oligo- or poly-carbodiimide with a matrix including at least one polyamide, in order to form a composition that has a good melt viscosity and is stable during transformation, in particular during extrusion.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.15/522,805, filed on Apr. 28, 2017, which is a U.S. national stage ofInternational Application No. PCT/FR2015/052987, filed on Nov. 5, 2015,which claims the benefit of French Application No. 1460666, filed onNov. 5, 2014. The entire contents of each of U.S. application Ser. No.15/522,805, International Application No. PCT/FR2015/052987, FrenchApplication No. 1460666 are hereby incorporated herein by reference intheir entirety.

TECHNICAL FIELD

The present invention relates to the use of at least one catalyst, of atleast one copper-based heat stabilizer and of at least one oligo- orpolycarbodiimide with a matrix comprising at least one thermoplasticpolymer, in particular a polyamide, in order to form a viscouscomposition which is stable in transformation, in particular inextrusion.

The present invention also relates to the viscous and stable compositionas defined above.

The invention also relates to the use of the above composition forforming a structure, such as:

a flexible pipe intended for the transportation of gas, for theexploitation of offshore oil deposits,

a flexible pipe for motor vehicles, in particular for the transportationof fuel (gasoline, diesel, biodiesel or ethanol), for refrigeration, forair conditioning, for ducts produced in particular by extrusion-blowmolding for supplying with air,

a hollow body, a molding or a sports item.

The invention also relates to the structures obtained from saidcompositions.

BACKGROUND

The exploitation of offshore oil deposits subjects the materialsemployed to extreme conditions, in particular the pipes connecting thevarious offshore devices of the platform and conveying the hydrocarbonsextracted, which are generally transported at high temperature and highpressure (for example, 700 bar).

During the operation of the plants, acute problems of mechanicalstrength, of thermal resistance and of chemical resistance of thematerials employed are thus posed. Such pipes must in particularwithstand oil which is hot, gas, water and mixtures of at least two ofthese products for periods of time which can reach 20 years.

Conventionally, these pipes comprise a nonleaktight internal metal layerformed by a helically wound profiled metal strip, such as an interlockedmetal strip. This internal metal layer, which gives shape to the pipe,is coated, generally by extrusion, with a polymer layer intended toconfer leaktightness. Other protective and/or reinforcing layers, suchas plies of metal fibers, thermoplastics and rubbers, can also bepositioned around the leaktight polymer layer.

For working temperatures below 40° C., the polymer is crosslinked ornoncrosslinked HDPE (high density polyethylene). For temperatures above40° C., polyamide is used and, for temperatures above 90° C., PVDF(polyvinylidene fluoride) is employed.

In view of the high cost of PVDF, and despite the implication of highertemperatures than those recommended, the choice of the polymer hasfallen on polyamides, such as PA11 and PA12, well known for their goodthermal behavior, their chemical resistance, in particular towardsolvents, their resistance to bad weather and to radiation, theirimpermeability to gases and liquids, and their nature as electricalinsulators.

These polyamides are already commonly used in the manufacture of pipesintended to convey hydrocarbons extracted from offshore or onshore oildeposits but exhibit, however, the disadvantage of aging excessivelyrapidly.

In order to overcome this disadvantage and thus to improve theresistance to aging of these polyamide-based pipes, the document US2003/0220449, on behalf of the applicant company, provides a compositioncomprising a mixture of PA, of plasticizer and of an elastomer chosenfrom nitrile/butadiene rubber (NBR) and hydrogenated nitrile/butadienerubber (H-NBR).

The use of an elastomer of the NBR or H-NBR type in the compositionsdescribed in the document US 2003/0220449 exhibits several advantages incomparison with the prior compositions solely based on polyamide andplasticizer.

In particular, the introduction of one or other of these elastomersmakes it possible to significantly increase the resistance to aging ofthe flexible pipes comprising such a layer, especially by limiting thecontent by weight of plasticizer.

However, H-NBR (or hydrogenated NBR) elastomers are expensive andnecessitate, like their nonhydrogenated NBR homologs, furthermorecarrying out a preliminary stage of grinding, adding a furtheradditional cost to that already generated by the NBR or H-NBR startingmaterial.

In order to overcome the above disadvantages, the applicant companydescribes, in the document WO 08/122743, the use of a compositioncomprising at least one semicrystalline polyamide, a functionalizedpolyolefin and a plasticizer for the manufacture of flexible pipes usedin particular for the exploitation of oil or gas deposits.

Furthermore, the extrusion of large-diameter pipes for theseapplications requires compositions exhibiting high melt viscosities butalso a stability in transformation (the residence time of the productduring its extrusion is at least 5 min or 300 seconds), and alsoresistance to thermal oxidation.

In order to obtain viscosities of this type, phosphoric catalysis makesit possible, under certain conditions (degree of catalysis, vacuum,humidity), to succeed in doing this but the product may continue tochange during the transformation. Furthermore, this postreactivity issensitive to the residual humidity of the granules.

In order to overcome this, the application US 2013/0171388 describes PAmaterials with chain extenders (Bruggolen® and/or Stabaxol®).Nevertheless, these compositions also have high polydispersity indicesand thus a large number of branchings, the consequence of which is toproduce high viscosities in solution.

Thus, the viscosity in solution is not representative of the meltviscosity due to the potential branchings in the polyamide.

Furthermore, the current polyamide compositions generally make possibleonly a working temperature of the pipes of 60° C. to 70° C., dependingon the pH or on the total acid number (TAN) of the fluid transported andon the acceptance criterion used.

It is thus necessary to find a compromise between these differentparameters and furthermore to increase the working temperature of thepipes.

SUMMARY

A first subject matter of the invention is thus the use of at least onecatalyst, of at least one copper-based heat stabilizer and of at leastone oligo- or polycarbodiimide with a matrix comprising at least onethermoplastic polymer, in particular a polyamide, in order to form aviscous composition which is stable in transformation, especially inextrusion.

A second subject matter of the invention is the provision of acomposition defined above and its use in forming a structure, such as:

a flexible pipe intended for the transportation of gas, for theexploitation of offshore oil deposits,

a flexible pipe for motor vehicles, in particular for the transportationof fuel (gasoline, diesel, biodiesel or ethanol), for refrigeration, forair conditioning, for ducts produced in particular by extrusion-blowmolding for supplying with air,

a hollow body,

Another subject matter of the invention is the provision of flexiblepipes defined above.

BRIEF DESCRIPTION OF THE FIGURE

FIG. 1 exhibits the oscillatory rheology at 270° C. (frequency: 10rad/s, 5% deformation, shearing 10 s⁻¹) from 0 to 30 minutes.

DETAILED DESCRIPTION

Use:

The present invention relates to the use of at least one catalyst, of atleast one copper-based heat stabilizer and of at least one oligo- orpolycarbodiimide with a matrix comprising at least one thermoplasticpolymer, in particular a polyamide, in order to form a composition whichexhibits a good melt viscosity and which is stable in transformation.

The inventors have found, entirely unexpectedly, that the combination ofthree components, namely a catalyst, a copper-based heat stabilizer andan oligo- or polycarbodiimide, makes it possible, in combination with athermoplastic polymer, in particular a polyamide, to obtain compositionswhich exhibit good viscosities, that is to say melt viscosities whichare sufficiently high to be able to be transformed, in particular byextrusion, without, however, increasing the viscosity in solution, inother words the inherent viscosity, said melt viscosity furthermorebeing sufficiently stable during transformation, in particular forextrusion.

The melt viscosity is determined by oscillatory rheology at 270° C. at10 rad/sec while flushing with nitrogen with 5% deformation and shearingof 10 sec⁻¹ on a Physica MCR301 device between two parallel plates witha diameter of 25 mm.

The inherent viscosity is determined according to the standard ISO307-2007 but in m-cresol instead of sulfuric acid, the temperature being20° C.

The expression “stable in transformation” means that the melt viscositydoes not change by more than 70% as a function of the time, andspecifically between 1 minute (time necessary to melt the product) andat least 30 minutes, in particular between 1 minute and 30 minutes.

Advantageously, the melt viscosity of said composition is substantiallyconstant between 1 minute and at least 5 minutes, especially between 1minute and 5 minutes.

“Substantially constant” should be understood as meaning that the meltviscosity does not change in a proportion of more than 20% between 1minute and at least 5 minutes, in particular between 1 minute and 5minutes.

The time of 5 minutes represents the residence time of the substance, inparticular in the extruder during the processing.

Advantageously, said composition additionally exhibits a resistance tothermal oxidation.

The expression “resistance to thermal oxidation” is characterized by thehalf life (in hours) of the materials. It corresponds to the time at theend of which the ISO 527-2 1BA test specimens, aged in air at 140° C.,have lost half of their initial elongation at break, measured accordingto the standard ISO 527-2 (2012).

Advantageously, the resistance to thermal oxidation is at least 80 days,in particular 100 days.

Advantageously, said composition exhibits a melt viscosity ofapproximately 13 000 to approximately 23 000 Pa·s, as determined byoscillatory rheology at 270° C. as defined above.

The inventors have thus found, entirely unexpectedly, that the keyfactor for the transformation of the composition of the invention is itsrheology and not the inherent viscosity. This is because, at constantinherent viscosity, it is noticed that only the compositions comprisingthe catalyst/copper-based heat stabilizer system and the oligo- orpolycarbodiimide make it possible to obtain a composition exhibiting anappropriate rheology, that is to say a melt viscosity comprised ofapproximately 13 000 to approximately 23 000 Pa·s, said viscosity alsobeing substantially constant and stable in transformation as definedabove.

The Catalyst:

The term “catalyst” denotes a polycondensation catalyst, such as aninorganic or organic acid.

Advantageously, the proportion by weight of catalyst is comprised ofapproximately 50 ppm to approximately 5000 ppm, especially ofapproximately 100 to approximately 3000 ppm, with respect to the totalweight of the composition.

Advantageously, the catalyst is chosen from phosphoric acid (H₃PO₄),phosphorous acid (H₃PO₃), hypophosphorous acid (H₃PO₂) or a mixture ofthese.

Advantageously, the present invention thus relates to the use definedabove of at least one catalyst, in a proportion by weight of catalystcomprised of approximately 50 ppm to approximately 5000 ppm, inparticular of approximately 100 to approximately 3000 ppm, with respectto the total weight of the composition, of at least one copper-basedheat stabilizer and of at least one oligo- or polycarbodiimide, with amatrix comprising at least one thermoplastic polymer, in particular apolyamide, said catalyst being chosen from phosphoric acid (H₃PO₄),phosphorous acid (H₃PO₃), hypophosphorous acid (H₃PO₂) or a mixture ofthese.

Advantageously, the catalyst is chosen from phosphoric acid (H₃PO₄),phosphorous acid (H₃PO₃) in a proportion comprised of approximately 100to approximately 3000 ppm.

The Copper-Based Stabilizer:

A well-known example is the mixture of CuI and KI, where the CuI:KIratio is typically between 1:2 and 1:15. An example of such a stabilizeris PolyAdd P201 from Polyad Services.

Fuller details with regard to copper-based stabilizers will be found inthe patent U.S. Pat. No. 2,705,227.

Advantageously, the copper-based stabilizer is chosen from copperhalides, copper acetate, copper halides or copper acetate as a mixturewith at least one alkali metal halide, and their mixtures, preferablymixtures of copper iodide and potassium iodide (CuI/KI).

The copper-based stabilizer can also be a Bruggolen® H3386.

Advantageously, the copper-based heat stabilizer used to form thecomposition defined above is in a proportion of approximately 0.05% toapproximately 1%, especially of approximately 0.05% to approximately0.3%, by weight, with respect to the total weight of the composition.

Preferably, the copper-based heat stabilizer is a mixture of potassiumiodide and copper iodide (KI/CuI).

Preferably, the mixture of potassium iodide and copper iodide of useaccording to the present invention is found in a ratio of 90/10 to70/30.

Advantageously, the present invention thus relates to the use definedabove of at least one catalyst, of at least one copper-based heatstabilizer in a proportion of approximately 0.05% to approximately 1%,in particular of approximately 0.05% to approximately 0.3%, by weight,with respect to the total weight of the composition, and of at least oneoligo- or polycarbodiimide, with a matrix comprising at least onethermoplastic polymer, in particular a polyamide, said copper-based heatstabilizer being a mixture of potassium iodide and copper iodide(KI/CuI), preferably in a ratio of 90/10 to 70/30.

Advantageously, the present invention relates to the use defined aboveof at least one catalyst, in a proportion by weight of catalystcomprised of approximately 50 ppm to approximately 5000 ppm, inparticular of approximately 100 to approximately 3000 ppm, with respectto the total weight of the composition, of at least one copper-basedheat stabilizer in a proportion of approximately 0.05% to approximately1%, in particular of approximately 0.05% to approximately 0.3%, byweight, with respect to the total weight of the composition, and of atleast one oligo- or polycarbodiimide, with a matrix comprising at leastone thermoplastic polymer, in particular a polyamide, said catalystbeing chosen from phosphoric acid (H₃PO₄), phosphorous acid (H₃PO₃),hypophosphorous acid (H₃PO₂) or a mixture of these, and saidcopper-based heat stabilizer being a mixture of potassium iodide andcopper iodide (KI/CuI), preferably in a ratio of 90/10 to 70/30.

Advantageously, the catalyst is chosen from phosphoric acid (H₃PO₄),phosphorous acid (H₃PO₃) in a proportion comprised of approximately 100to approximately 3000 ppm.

The Carbodiimide:

The carbodiimide represents a conventionally known carbodiimide oligomerand polymer and can be prepared by polymerization of diisocyanates.

This reaction can be accelerated by catalysts and products withelimination of carbon dioxide (J. Org. Chem., 28, 2069 (1963); J. Am.Chem. Soc. 84, 3673 (1962); Chem. Rev., 81, 589 (1981); Ange. Chem., 93,855 (1981)).

The reactants of the NCO end groups can comprise a reactive compound CH,NH or OH, for example malonic acid esters, caprolactam, alcohols orphenols.

In an alternative form, mixtures of mono- and diisocyanates can bepolymerized in order to obtain oligo- or polycarbodiimides containingessentially unreactive end groups.

The carbodiimide used is an oligo- or polycarbodiimide of generalformula:

$R_{1}—\; N\begin{matrix}— \\—\end{matrix}C\begin{matrix}— \\—\end{matrix}{N\left( {—\; R_{2}—\; N\begin{matrix}— \\—\end{matrix}C\begin{matrix}— \\—\end{matrix}N\; —} \right)}_{n}—\; R_{3}$

in which R₁ and R₃ represent C₁ to C₂₀ alkyls, C₅ to C₂₀ cycloalkyls,aryls having from 6 to 20 carbon atoms or aralkyls having from 7 to 20carbon atoms, each optionally being substituted by an isocyanate groupoptionally comprising a CH, an NH or a reactive compound OH; R₂represents an alkylene group having from 2 to 20 carbon atoms, acycloalkylene group having from 5 to 20 carbon atoms, an arylene grouphaving from 6 to 20 carbon atoms or an aralkylene group having from 7 to20 carbon atoms;

n=1 to 100, preferably from 2 to 80 and preferably from 3 to 70.

The oligo- or polycarbodiimide can be a homopolymer or a copolymer, forexample a copolymer of 2,4-diisocyanato-1,3,5-triisopropylbenzene and1,3-diisocyanato-3,4-diisopropylbenzene.

The oligo- or polycarbodiimide can also be chosen from those describedin U.S. Pat. No. 5,360,888.

The oligo- or polycarbodiimide can also be cyclic, in particular TCC(Teijin cyclic carbodiimide, sold by Teijin).

The appropriate oligo- and polycarbodiimides can be obtained fromcommercially available sources, such as Rhein Chemie, Raschig, Ziko orTeijin.

Advantageously, the proportion by weight of oligo- or polycarbodiimideused is comprised of approximately 0.1 to approximately 3%, especiallyof 0.5 to 2%, in particular approximately equal to 1%, with respect tothe total weight of the composition.

Advantageously, the oligo- or polycarbodiimide is chosen from aStabilizer, especially Stabilizer® 9000, a Stabaxol®, in particular aStabaxol® P, especially Stabaxol® P100 or Stabaxol® P400, or a mixtureof these.

Advantageously, the present invention thus relates to the use definedabove of at least one catalyst, of at least one copper-based heatstabilizer and of at least one oligo- or polycarbodiimide in aproportion of approximately 0.1 to approximately 3%, especially of 0.5to 2%, in particular approximately equal to 1%, by weight, with respectto the total weight of the composition, with a matrix comprising atleast one thermoplastic polymer, in particular a polyamide, said oligo-or polycarbodiimide being chosen from a Stabilizer, especiallyStabilizer® 9000, a Stabaxol®, in particular a Stabaxol® P, especiallyStabaxol® P100 or Stabaxol® P400, or a mixture of these.

Advantageously, the present invention relates to the use defined aboveof at least one catalyst, in a proportion by weight of catalystcomprised of approximately 50 ppm to approximately 5000 ppm, especiallyof approximately 100 to approximately 3000 ppm, with respect to thetotal weight of the composition, of at least one copper-based heatstabilizer and of at least one oligo- or polycarbodiimide in aproportion of approximately 0.1 to approximately 3%, especially of 0.5to 2%, in particular approximately equal to 1%, by weight, with respectto the total weight of the composition, with a matrix comprising atleast one thermoplastic polymer, in particular a polyamide, saidcatalyst being chosen from phosphoric acid (H₃PO₄), phosphorous acid(H₃PO₃), hypophosphorous acid (H₃PO₂) or a mixture of these, and saidoligo- or polycarbodiimide being chosen from a Stabilizer, especiallyStabilizer® 9000, a Stabaxol®, in particular a Stabaxol® P, especiallyStabaxol® P100 or Stabaxol® P400, or a mixture of these.

Advantageously, the catalyst is chosen from phosphoric acid (H₃PO₄),phosphorous acid (H₃PO₃) in a proportion comprised of approximately 100to approximately 3000 ppm.

Advantageously, the present invention relates to the use defined aboveof at least one catalyst, of at least one copper-based heat stabilizerin a proportion of approximately 0.05% to approximately 1%, especiallyof approximately 0.05% to approximately 0.3%, by weight, with respect tothe total weight of the composition, and of at least one oligo- orpolycarbodiimide in a proportion of approximately 0.1 to approximately3%, especially of 0.5 to 2%, in particular approximately equal to 1%, byweight, with respect to the total weight of the composition, with amatrix comprising at least one thermoplastic polymer, in particular apolyamide, said copper-based heat stabilizer being a mixture ofpotassium iodide and copper iodide (KI/CuI), preferably in a ratio of90/10 to 70/30, and said oligo- or polycarbodiimide being chosen from aStabilizer, especially Stabilizer® 9000, a Stabaxol®, in particular aStabaxol® P, especially Stabaxol® P100 or Stabaxol® P400, or a mixtureof these.

Advantageously, the present invention thus relates to the use definedabove of at least one catalyst, in a proportion by weight of catalystcomprised of approximately 50 ppm to approximately 5000 ppm, especiallyof approximately 100 to approximately 3000 ppm, with respect to thetotal weight of the composition, of at least one copper-based heatstabilizer in a proportion of approximately 0.05% to approximately 1%,especially of approximately 0.05% to approximately 0.3%, by weight, withrespect to the total weight of the composition, and of at least oneoligo- or polycarbodiimide in a proportion of approximately 0.1 toapproximately 3%, especially of 0.5 to 2%, in particular approximatelyequal to 1%, by weight, with respect to the total weight of thecomposition, with a matrix comprising at least one thermoplasticpolymer, in particular a polyamide, said catalyst being chosen fromphosphoric acid (H₃PO₄), phosphorous acid (H₃PO₃), hypophosphorous acid(H₃PO₂) or a mixture of these, said copper-based heat stabilizer being amixture of potassium iodide and copper iodide (KI/CuI), preferably in aratio of 90/10 to 70/30, said oligo- or polycarbodiimide being chosenfrom a Stabilizer, especially Stabilizer® 9000, a Stabaxol®, inparticular a Stabaxol® P, especially Stabaxol® P100 or Stabaxol® P400,or a mixture of these.

Advantageously, the catalyst is chosen from phosphoric acid (H₃PO₄),phosphorous acid (H₃PO₃) in a proportion comprised of approximately 100to approximately 3000 ppm.

The Thermoplastic Polymer:

As regards the thermoplastic polymer, it can be chosen from polyamidesor mixtures of polyamides.

The nomenclature used to define polyamides is described in the standardISO 1874-1:1992 “Plastics—Polyamide (PA) molding and extrusionmaterials—Part 1: Designation”, in particular on page 3 (tables 1 and2), and is well known to a person skilled in the art.

The polyamide according to the present invention can have ahomopolyamide or copolyamide structure.

Homopolyamide is understood to mean, within the meaning of the presentinvention, a polyamide which consists only of the repetition of a singleunit.

Copolyamide is understood to mean, within the meaning of the presentinvention, a polyamide which consists of the repetition of at least twounits of different chemical structure. This copolyamide can exhibit arandom, alternating or block structure.

The polyamide according to the present invention can comprise one ormore units with a structure chosen from amino acids, lactams and(diamine).(diacid) units.

When the polyamide comprises an amino acid in its structure, it can bechosen from 9-aminononanoic acid (A=9), 10-aminodecanoic acid (A=10),10-aminoundecanoic acid (A=11), 12-aminododecanoic acid (A=12) and11-aminoundecanoic acid (A=11) and its derivatives, in particularN-heptyl-11-aminoundecanoic acid, A denoting the number of carbon atomsin the unit.

When the polyamide comprises a lactam, it may be chosen frompyrrolidinone, 2-piperidinone, caprolactam, enantholactam,caprylolactam, pelargolactam, decanolactam, undecanolactam andlauryllactam (A=12).

When the polyamide comprises is a unit corresponding to the formula (Cadiamine).(Cb diacid), Ca and Cb denoting the number of carbon atomsrespectively in the diamine and the diacid, the (Ca diamine) unit ischosen from linear or branched aliphatic diamines, cycloaliphaticdiamines and alkylaromatic diamines.

When the diamine is aliphatic and linear, of formula H₂N—(CH₂)_(a)—NH₂,the (Ca diamine) monomer is preferably chosen from butanediamine (a=4),pentanediamine (a=5), hexanediamine (a=6), heptanediamine (a=7),octanediamine (a=8), nonanediamine (a=9), decanediamine (a=10),undecanediamine (a=11), dodecanediamine (a=12), tridecanediamine (a=13),tetradecanediamine (a=14), hexadecanediamine (a=16), octadecanediamine(a=18), octadecenediamine (a=18), eicosanediamine (a=20),docosanediamine (a=22) and diamines obtained from fatty acids.

When the diamine is aliphatic and branched, it can comprise one or moremethyl or ethyl substituents on the main chain. For example, the (Cadiamine) monomer can advantageously be chosen from2,2,4-trimethyl-1,6-hexanediamine, 2,4,4-trimethyl-1,6-hexanediamine,1,3-diaminopentane, 2-methyl-1,5-pentanediamine or2-methyl-1,8-octanediamine.

When the (Ca diamine) monomer is cycloaliphatic, it is chosen frombis(3,5-dialkyl-4-aminocyclohexyl)methane,bis(3,5-dialkyl-4-aminocyclohexyl)ethane,bis(3,5-dialkyl-4-aminocyclohexyl)propane,bis(3,5-dialkyl-4-aminocyclohexyl)butane,bis(3-methyl-4-aminocyclohexyl)methane (BMACM or MACM),bis(p-aminocyclohexyl)methane (PACM), isopropylidenedi(cyclohexylamine)(PACP), isophoronediamine (a=10), piperazine (a=4) oraminoethylpiperazine. It can also comprise the following carbonbackbones: norbornylmethane, cyclohexylmethane, dicyclohexylpropane,di(methylcyclohexyl) or di(methylcyclohexyl)propane. A nonexhaustivelist of these cycloaliphatic diamines is given in the publication“Cycloaliphatic Amines” (Encyclopaedia of Chemical Technology,Kirk-Othmer, 4th Edition (1992), pp. 386-405).

When the (Ca diamine) monomer is alkylaromatic, it is chosen from1,3-xylylenediamine and 1,4-xylylenediamine.

The (Cb diacid) unit is chosen from linear or branched aliphaticdiacids, cycloaliphatic diacids and aromatic diacids.

When the (Cb diacid) monomer is aliphatic and linear, it is chosen fromsuccinic acid (b=4), pentanedioic acid (b=5), adipic acid (b=6),heptanedioic acid (b=7), octanedioic acid (b=8), azelaic acid (b=9),sebacic acid (b=10), undecanedioic acid (b=11), dodecanedioic acid(b=12), brassylic acid (b=13), tetradecanedioic acid (b=14),hexadecanedioic acid (b=16), octadecanedioic acid (b=18),octadecenedioic acid (b=18), eicosanedioic acid (b=20), docosanedioicacid (b=22) and fatty acid dimers containing 36 carbons.

The fatty acid dimers mentioned above are dimerized fatty acids obtainedby oligomerization or polymerization of unsaturated monobasic fattyacids bearing a long hydrocarbon chain (such as linoleic acid and oleicacid), as described in particular in the document EP 0471566.

When the diacid is cycloaliphatic, it can comprise the following carbonbackbones: norbornylmethane, cyclohexylmethane, dicyclohexylmethane,dicyclohexylpropane, di(methylcyclohexyl) ordi(methylcyclohexyl)propane.

When the diacid is aromatic, it is chosen from terephthalic acid(denoted T), isophthalic acid (denoted I) and naphthalenic diacids.

Advantageously, the thermoplastic polymer is a polyamide chosen from analiphatic polyamide, a cycloaliphatic polyamide, an aromatic polyamideor a mixture of these.

Advantageously, the polyamide exhibits a M.p. comprised of 160° C. to290° C., determined according to the standard ISO 11357-3 (2013).

Advantageously, the proportion of polyamide is comprised ofapproximately 95.5 to approximately 99.845%.

Preferably, the polyamide of use according to the invention is chosenfrom PA 6, PA 11, PA 12, PA 6.10, PA 6.6, PA 6.12, PA 10.10, PA 10.12,PA 11/10.T, PA 11/6.T, 12/10.T, 6.10/10.T, 6.12/10.T, 10.10/10.T,10.12/10.T, 11/6.T/10.T, 12.12/10.T, 12/6.10/10.T, 12/6.12/10.T,12/10.10/10.T, 12/10.12/10.T and 12/12.12/10.T.

Advantageously, the polyamide is chosen from: PA 11, PA 12, PA 11/10.T,PA 10.10, PA 10.12 and the copolyamides 11/12 having either more than90% of units 11 or more than 90% of units 12, preferably from PA 11, PA12, PA 11/10.T, PA 10.10 and PA 10.12.

The Polyolefin:

Advantageously, the thermoplastic polymer, in particular the polyamide,can contain at least one polyolefin.

The polyolefin may be functionalized or nonfunctionalized or be amixture of at least one functionalized and/or at least onenonfunctionalized. To simplify, functionalized polyolefins (B1) andnonfunctionalized polyolefins (B2) have been described later.

The functionalized polyolefin (B1) can be chosen from the following(co)polymers, grafted with maleic anhydride, in which the degree ofgrafting is, for example, from 0.01% to 5% by weight:

-   -   PE, PP, copolymers of ethylene with propylene, butene, hexene or        octene containing, for example, from 35% to 80% by weight of        ethylene;    -   ethylene/α-olefin copolymers, such as ethylene/propylene, EPRs        (abbreviation of ethylene/propylene rubbers) and        ethylene/propylene/dienes (EPDMs),    -   styrene/ethylene-butene/styrene (SEBS),        styrene/butadiene/styrene (SBS), styrene/isoprene/styrene (SIS)        or styrene/ethylene-propylene/styrene (SEPS) block copolymers;    -   copolymers of ethylene and vinyl acetate (EVA), containing up to        40% by weight of vinyl acetate;    -   copolymers of ethylene and alkyl (meth)acrylate, containing up        to 40% by weight of alkyl (meth)acrylate;    -   copolymers of ethylene and vinyl acetate (EVA) and alkyl        (meth)acrylate, containing up to 40% by weight of comonomers;    -   maleated polyolefins, such as Tafmer® MH5020, Tafmer® 610MP,        Tafmer® MD715, Orevac® IM800, Exxelor® VA 1801 and 1803, and        Fusabond.

The Tafmer® products are sold by Mitsui Chemicals, the Orevac® productsby the applicant company and the Exxelor products by Exxon MobilChemicals.

The functionalized polyolefin (B1) can also be a copolymer or terpolymerof at least the following units: (1) ethylene, (2) alkyl (meth)acrylateor saturated carboxylic acid vinyl ester and (3) anhydride, such asmaleic anhydride or (meth)acrylic acid anhydride.

Mention may be made, as examples of functionalized polyolefins of thelatter type, of the following copolymers, where ethylene preferablyrepresents at least 60% by weight and where the termonomer (thefunction) represents, for example, from 0.1% to 10% by weight of thecopolymer:

-   -   ethylene/alkyl (meth)acrylate/maleic anhydride or (meth)acrylic        acid copolymers;    -   ethylene/vinyl acetate/maleic anhydride copolymers;    -   ethylene/vinyl acetate or alkyl (meth)acrylate/maleic anhydride        or (meth)acrylic acid.

The term “alkyl (meth)acrylate” in (B1) or (B2) denotes C₁ to C₁₂ alkylmethacrylates and acrylates and can be chosen from methyl acrylate,ethyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexylacrylate, cyclohexyl acrylate, methyl methacrylate and ethylmethacrylate.

The abovementioned copolymers, (B1) and (B2), can be copolymerized inrandom or block fashion and exhibit a linear or branched structure.

The molecular weight, the MFI index and the density of these polyolefinscan also vary to a large extent, which will be appreciated by a personskilled in the art. MFI is the abbreviation for Melt Flow Index. It ismeasured according to the standard ASTM 1238-13.

Advantageously, the nonfunctionalized polyolefins (B2) are chosen frompolypropylene homopolymers or copolymers, and any homopolymer ofethylene or copolymer of ethylene and a comonomer of α-olefin type, suchas propylene, butene, hexene, octene or 4-methyl-1-pentene. Mention maybe made, for example, of PPs, high-density PEs, medium-density PEs,linear low-density PEs, low density PEs or very low density PEs. Thesepolyethylenes are known by a person skilled in the art to be producedaccording to a “radical” process, according to a catalysis of“Ziegler-Natta” type or, more recently, according to a “metallocene”catalysis.

Advantageously, the functionalized polyolefins (B1) are chosen from anypolymer comprising α-olefin units and units bearing polar reactivefunctional groups, such as carboxylic acid or carboxylic acid anhydridefunctional groups. Mention may be made, as examples of such polymers, ofpolymers of ethylene and alkyl acrylate, such as the Lucalen® products,terpolymers of ethylene, alkyl acrylate and maleic anhydride, such asthe Lotader® products from the applicant company, or polyolefins graftedby maleic anhydride, such as the Orevac® products from the applicantcompany, or terpolymers of ethylene, octene and maleic anhydride knownas Fusabond® 493 from Dupont, and also terpolymers of ethylene, alkylacrylate and (meth)acrylic acid.

The Additives:

The thermoplastic polymer, in particular the polyamide, can contain atleast one usual additive, such as heat stabilizers, glass fibers, carbonfibers, a flame retardant, talc, a nucleating agent, a plasticizer, acolorant, a fluorinated agent, a lubricant, a stearate, such as zincstearate, calcium stearate or magnesium stearate, and also anotherpolyamide, catalyzed or noncatalyzed, different from that used above.

It should be noted that said heat stabilizer is different from thecopper-based heat stabilizer described above and consequently does notcontain copper.

The heat stabilizer can be an organic stabilizer or more generally acombination of organic stabilizers, such as a primary antioxidant ofphenol type (for example of the type of that of Irganox® 245 or 1098 or1010 from BASF), a secondary antioxidant of phosphite type, and indeedeven optionally other stabilizers, such as a HALS, which means HinderedAmine Light Stabilizer (for example Tinuvin® 770 from BASF), a UVinhibitor (for example Tinuvin® 312 from BASF), a phenol stabilizer or aphosphorus-based stabilizer. Use may also be made of antioxidants ofamine type, such as Naugard® 445(4,4′-bis(α,α-dimethylbenzyl)diphenylamine) from Crompton or Flexamine®from Addivant, or else of polyfunctional stabilizers, such as Nylostab®S-EED from Clariant.

Advantageously, the present invention relates to one of the uses definedabove in which at least one polyolefin and/or at least one additive areoptionally present, in particular up to 30% each by weight, with respectto the total weight of the composition.

Advantageously, the present invention relates to one of the uses definedabove in which a polyolefin is also present, in particular fromapproximately 1 to approximately 15% by weight, with respect to thetotal weight of the composition. Advantageously, the polyolefin ischosen from a maleated EPR, in particular Exxelor® VA 1801 and Exxelor®VA1803, sold by ExxonMobil, a Fusabond®, in particular Fusabond® 493from DuPont, and Tafmer® MH5020, Tafmer® 610MP and Tafmer® MD715 fromMitsui Chemicals.

Advantageously, the present invention relates to one of the uses definedabove in which at least one additive is optionally present, inparticular up to 30%.

Advantageously, the present invention relates to one of the uses definedabove in which an additive is also present, in particular fromapproximately 0.1 to approximately 1% by weight, with respect to thetotal weight of the composition.

Advantageously, the additive is a heat stabilizer.

Advantageously, the present invention relates to one of the uses definedabove in which a polyolefin is present, especially from approximately 1to approximately 15% by weight, with respect to the total weight of thecomposition, and at least one additive is also present, especially fromapproximately 0.1 to approximately 30%, especially from approximately0.1 to approximately 20% and in particular from approximately 0.1 toapproximately 10% by weight, with respect to the total weight of thecomposition.

Advantageously, the present invention relates to one of the uses definedabove in which a polyolefin is present, in particular from approximately1 to approximately 15% by weight, with respect to the total weight ofthe composition, and an additive is also present, especially fromapproximately 0.1 to approximately 1% by weight, with respect to thetotal weight of the composition.

Advantageously, the polyolefin is chosen from a maleated EPR, inparticular EPR 1801, and a Fusabond®, especially Fusabond® 493, and theadditive is a heat stabilizer.

The Plasticizers:

As regards the plasticizer, it is chosen from benzenesulfonamidederivatives, such as n-butylbenzenesulfonamide (BBSA) orN-(2-hydroxypropyl)benzenesulfonamide (HP-BSA) from Proviron,ethyltoluenesulfonamide or N-cyclohexyltoluenesulfonamide fromSigma-Aldrich; esters of hydroxybenzoic acids, such as 2-ethylhexylpara-hydroxybenzoate (EHPD) from Ueno Fine Chemicals and 2-decylhexylpara-hydroxybenzoate (HD-PB) from Kao; esters or ethers oftetrahydrofurfuryl alcohol, such as oligoethyleneoxytetrahydrofurfurylalcohol; and esters of citric acid or of hydroxymalonic acid, such asoligoethyleneoxy malonate. n-Butylbenzenesulfonamide (BBSA) is aparticularly preferred plasticizer. It would not be departing from thescope of the invention to use a mixture of plasticizers. The plasticizercan be introduced into the polyamide during the polycondensation orsubsequently. The proportion of plasticizer can be from 0 to 15% byweight.

Advantageously, the plasticizer used is a benzenesulfonamide derivative,such as n-butylbenzenesulfonamide (BBSA).

Advantageously, the present invention relates to one of the uses definedabove in which a plasticizer is also present, in particular fromapproximately 1 to approximately 10% by weight, with respect to thetotal weight of the composition.

Advantageously, the present invention relates to one of the uses definedabove in which a polyolefin is present, especially from approximately 1to approximately 15% by weight, with respect to the total weight of thecomposition, at least one additive is also present, especially fromapproximately 1 to approximately 10% by weight, with respect to thetotal weight of the composition, and also a plasticizer, especially fromapproximately 1 to approximately 10% by weight, with respect to thetotal weight of the composition.

Advantageously, the present invention relates to one of the uses definedabove in which a polyolefin is present, especially from approximately 1to approximately 15% by weight, with respect to the total weight of thecomposition, an additive is also present, especially from approximately0.1 to approximately 1% by weight, with respect to the total weight ofthe composition, and also a plasticizer, especially from approximately 1to approximately 10% by weight, with respect to the total weight of thecomposition.

Advantageously, the polyolefin is chosen from a maleated EPR, inparticular EPR® 1801, and a Fusabond®, especially Fusabond® 493, and theadditive is a heat stabilizer, and the plasticizer is abenzenesulfonamide derivative, such as n-butylbenzenesulfonamide (BBSA).

Compositions:

According to another aspect, the present invention relates to a viscouscomposition which is stable in transformation as defined above,characterized in that it comprises, with respect to the total weight ofthe composition:

a. 20.5 to 99.845% by weight of at least one polyamide as defined above;

b. 0.005 to 0.5% by weight of at least one catalyst;

c. 0.05 to 1% by weight of at least one copper-based heat stabilizer;

d. 0.1 to 3% by weight of at least one oligo- or polycarbodiimide;

e. 0 to 15% of at least one plasticizer;

f. 0 to 30% of at least one polyolefin;

g. 0 to 30% of at least one additive.

According to this aspect, putting aside the proportion of polyamidepresent in the composition, which is limited from 20.5 to 99.845% byweight, with respect to the total weight of the composition, thecatalyst, the copper-based heat stabilizer, the oligo- orpolycarbodiimide, the plasticizer, the polyolefin and the additive areas defined above for the use, and the different combinations andalternative forms relating to the proportions of these differentconstituents thus apply to these compositions as such.

Said composition exhibits all the properties defined above, namelyexhibiting a good melt viscosity which is stable in transformation,especially in extrusion, between 1 minute and at least 30 minutes,especially between 1 minute and 30 minutes, and especially said meltviscosity of said composition is substantially constant between 1 minuteand at least 5 minutes, especially between 1 minute and 5 minutes. Saidcomposition additionally exhibits a resistance to thermal oxidation. Itexhibits in particular a melt viscosity of approximately 13 000 toapproximately 23 000 Pa·s, as determined by oscillatory rheology at 270°C. (plate-plate), especially for at least 30 minutes, in particular for30 minutes.

Advantageously, said composition exhibits a resistance to hydrolysis.

The expression “resistance to hydrolysis” means that the half life ofthe pipes (in hours), which corresponds to the time at the end of whichthe pipes tested break, after exposure to hot water or a mixture ofwater and ethylene glycol at 140° C., with an elongation at break testaccording to the standard ISO 527-2 (2012), is at least 40 days. Inother words, it is the time in order to have 50% absolute of elongationat break of the pipes.

Advantageously, said composition exhibits a resistance to thermaloxidation and a resistance to hydrolysis.

Thus, the composition of the invention, whether or not it comprisespolyolefins and/or plasticizers and/or additives, exhibits a meltviscosity of approximately 13 000 to approximately 23 000 Pa·s for atleast 30 minutes, this being the case whatever the inherent viscosity ofthe composition devoid of said polyolefins, plasticizers and additives.

The compositions of the invention make it possible to facilitate theextrusion of large pipes, in particular for gas pipes or theexploitation of offshore oil.

Furthermore, the compositions of the invention are particularly stableto thermal behavior and to hydrolysis.

Advantageously, the polyamide is chosen from PA11, PA12, PA 11/10.T, PA10.10, PA 10.12 and copolyamides 11/12 having either more than 90% ofunits 11 or more than 90% of units 12, especially from PA11, PA12, PA11/10.T, PA 10.10 and PA 10.12, the catalyst is chosen from phosphoricacid (H₃PO₄), phosphorous acid (H₃PO₃), hypophosphorous acid (H₃PO₂), ora mixture of these, the copper-based heat stabilizer is a mixture ofpotassium iodide and copper iodide, the oligo- or polycarbodiimide ischosen from a Stabilizer, especially Stabilizer® 9000, a Stabaxol®, inparticular a Stabaxol® P, especially Stabaxol® P100 or Stabaxol® P400,or a mixture of these.

Advantageously, the composition comprises:

-   -   a. 95.5 to 99.845% by weight of at least one polyamide as        defined above;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide.

More advantageously, said composition comprises or consists of:

-   -   a. 85.5 to 98.845% by weight of at least one polyamide as        defined above;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 10% by weight of at least one additive.

Advantageously, the additives of said composition a., b., c., d. and e.which is defined above are a mixture of a colorant in the form of amasterbatch, of a UV stabilizer, of a nucleating agent and of heatstabilizers.

This composition can be in the granule or powder form and is suitablefor numerous applications.

Advantageously, the composition comprises or consists of:

-   -   a. 80.5 to 98.845% by weight of at least one polyamide as        defined above;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 15% of at least one plasticizer.

More advantageously, said composition comprises or consists of:

-   -   a. 70.5 to 97.845% by weight of at least one polyamide as        defined above;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 15% of at least one plasticizer.    -   f. 1 to 10% by weight of at least one additive.

Advantageously, the additives of said composition a., b., c., d., e. andf. which is defined above are a mixture of a colorant in the form of amasterbatch, of a UV stabilizer, of a nucleating agent and of heatstabilizers.

This composition can be in the granule or powder form and is moreparticularly suitable for the molding of parts, in particular for sport.

Advantageously, the composition consists of:

-   -   a. 55.5 to 98.745% by weight of at least one polyamide as        defined above;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 30% of at least one polyolefin;    -   f. 0.1 to 10% of at least one additive.

Advantageously, the additives of said composition a., b., c., d., e. andf. which is defined above are a mixture of a colorant in the form of amasterbatch, of a UV stabilizer, of a nucleating agent and of heatstabilizers.

Advantageously, the composition consists of:

-   -   a. 64.5 to 98.745% by weight of at least one polyamide as        defined above;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 30% of at least one polyolefin;    -   f. 0.1 to 1% of at least one additive.

These last two compositions can be in the granule or powder form and aremore particularly suitable for the extrusion of gas pipes.

Advantageously, the composition consists of:

-   -   a. 40.50 to 97.745% by weight of at least one polyamide as        defined in claim 12 to 14;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 15% of at least plasticizer;    -   f. 1 to 30% of at least one polyolefin;    -   g. 0.1 to 10% of at least one additive.

Advantageously, the additives of said composition a., b., c., d., e., f.and g. which is defined above are a mixture of a colorant in the form ofa masterbatch, of a UV stabilizer, of a nucleating agent and of heatstabilizers.

Advantageously, the composition consists of:

-   -   a. 49.50 to 97.745% by weight of at least one polyamide as        defined in claim 12 to 14;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 15% of at least plasticizer;    -   f. 1 to 30% of at least one polyolefin;    -   g. 0.1 to 1% of at least one additive.

These last two compositions can be in the granule or powder form and aremore particularly suitable for the extrusion of pipes for theexploitation of offshore oil deposits or of pipes for use under a motorvehicle hood or for the molding of parts, in particular for sport.

Advantageously, the polyamide of the compositions of the invention ischosen from an aliphatic polyamide, a cycloaliphatic polyamide, anaromatic polyamide or a mixture of these.

Use of the Composition:

According to another aspect, the present invention relates to the use ofa composition as defined above for forming a structure, such as:

-   -   a flexible pipe intended for the transportation of gas, for the        exploitation of offshore oil deposits,    -   a flexible pipe for motor vehicles, in particular for the        transportation of fuel (gasoline, diesel, biodiesel or ethanol),        for refrigeration, for air conditioning, for ducts produced in        particular by extrusion-blow molding for supplying with air,    -   a hollow body, a molding or a sports item.

According to this aspect, just like above, the catalyst, thecopper-based heat stabilizer, the oligo- or polycarbodiimide, theplasticizer, the polyolefin and the additive are as defined above forthe use or the composition, and the different combinations andalternative forms relating to the proportions of these differentconstituents defined above thus apply to the use of these compositionsfor forming said structure.

The flexible pipe intended for the transportation of gas or for theexploitation of offshore oil deposits exhibits a good resistance tothermal oxidation and a resistance to hydrolysis and in particular aworking temperature of at least 70° C. for 20 years.

Advantageously, the compositions used for forming a structure which is aflexible pipe intended for the exploitation of offshore oil deposits canalso be used for forming a structure which is a flexible pipe for motorvehicles, in particular for the transportation of fuel (gasoline,diesel, biodiesel or ethanol), for refrigeration, for air conditioningor for ducts produced in particular by extrusion-blow molding forsupplying with air.

Structure:

According to another aspect, the present invention relates to a flexiblepipe intended for the transportation of gas or for the exploitation ofoffshore oil deposits, or for motor vehicles, in particular for thetransportation of fuel (gasoline, diesel, biodiesel or ethanol), forrefrigeration, for air conditioning or for supplying with air as definedabove, comprising at least one layer of a composition as defined above.

According to this aspect, just like above, the catalyst, thecopper-based heat stabilizer, the oligo- or polycarbodiimide, theplasticizer, the polyolefin and the additive are as defined above forthe use or the composition, and the different combinations andalternative forms relating to the proportions of these differentconstituents defined above thus apply to the pipes as such.

Advantageously, the flexible pipe defined above is characterized in thatsaid layer is the layer in contact with the fluid and the composition isas defined above for forming a structure which is a flexible pipeintended for the transportation of gas.

Advantageously, said pipe intended for the transportation of gas is amonolayer pipe.

Advantageously, said flexible pipe intended for the transportation ofgas is characterized in that it can additionally comprise at least oneother layer, in particular made of thermoplastic.

Said pipe can furthermore comprise a reinforcer, in particular areinforcer chosen from a metal reinforcer, a reinforcer made of glassfiber, a reinforcer made of carbon fiber and a reinforcer made of aramidfiber. Advantageously, the flexible pipe defined above of the inventionis characterized in that said layer is the internal layer of a flexiblepipe intended for the exploitation of offshore oil deposits, thecomposition being as defined above, for forming a structure which is aflexible pipe intended for the exploitation of offshore oil deposits.

The structure of pipes intended for the exploitation of offshore oildeposits is described in particular in the international application WO2013/128097 and corresponds especially to the pipe comprising the layers2 to 8 of FIG. 1 of said international application WO 2013/128097.

Said internal layer corresponds in this case to the layer 3 of the pipeof the international application WO 2013/128097, that is to say thepressure sheath or sealing sheath.

Advantageously, the flexible pipe defined above is characterized in thatsaid layer is the external layer of a flexible pipe intended for theexploitation of offshore oil deposits, the composition being as definedabove, for forming a structure which is a flexible pipe intended for theexploitation of offshore oil deposits.

Said external layer corresponds in this case to the layer (8) of thepipe of the international application WO 2013/128097.

Advantageously, the flexible pipe of the invention intended for theexploitation of offshore oil deposits comprises an internal layer (3)defined above and an external layer (8) defined above, said internal andexternal layers consisting of the same composition of the invention oreach consisting of a different composition of the invention.

It would not be departing from the scope of the invention if one of thelayers (3) or (8) consisted of a thermoplastic other than that of theinvention as described in WO 2013/128097, in particular anotherpolyamide.

Advantageously, the flexible pipe of the invention intended for theexploitation of offshore oil deposits consists of the layers 2/3/4/6/7/8described in WO 2013/128097, the layers 3 and 8 being as defined above,and the layer 2 corresponding to the internal carcass in contact withthe oil, the layer 4 corresponding to an intermediate sheath made ofpolyethylene or polypropylene and the layers 6 and 7 corresponding totensile armor layers.

Advantageously, the flexible pipe of the invention intended for theexploitation of offshore oil deposits consists of the layers2/3/4/5/6/7/8 described in WO 2013/128097, the layers 2 to 4 and 6 to 8being as defined above and the layer (5) corresponding to the pressurevault.

Advantageously, the flexible pipe of the invention intended for theexploitation of offshore oil deposits consists of the layers30/40/50/80/90 described in the application US 2009/0308478.

Said internal layer defined above consisting of compositions of theinvention can correspond to the internal layer 30.

Said external layer defined above consisting of compositions of theinvention can correspond to the external layer 90 of said application US2009/0308478.

The other layers are as defined in the application US 2009/0308478.

Advantageously, the flexible pipe as defined above for motor vehicles,in particular for the transportation of gasoline, for refrigeration, forair conditioning, for ducts produced in particular by extrusion-blowmolding for supplying with air, is characterized in that it comprises atleast one layer consisting of a composition as defined for forming astructure which is a flexible pipe intended for the exploitation ofoffshore oil deposits.

The pipe for air conditioning is in particular suitable for thetransportation of a refrigerant and in particular of the gas R-1234yf orcis- or trans-1234-ze), used in particular in the field of motor vehicleair conditioning or stationary air conditioning.

EXAMPLES

The invention will now be illustrated using the following examples,which are not, however, limiting of the invention.

The graph in FIG. 1 exhibits the analysis time in seconds on theabscissa and the viscosity in Pa·s on the ordinate.

At 1800 seconds, from the top downwards:Catalyzed PA 11 (600 ppm H₃PO₄).Catalyzed PA 11 (600 ppm H₃PO₄)+1% Stabilizer 9000.Catalyzed PA 11 (600 ppm H₃PO₄)+1% Stabilizer 9000+0.25% iodine 201:curve of the invention, the only one having a viscosity of between 13000 and 23 000 Pa·s.Non-catalyzed PA 12+1% Stabilizer 9000+0.25% iodine 201.

Non-catalyzed PA 11+1% Stabilizer 9000.

Catalyzed PA 11 (600 ppm H₃PO₄)+0.25% iodine 201.

Non-catalyzed PA 11. EXAMPLES Products Used

The polyamides used are PA 11 (Besno, sold by Arkema), PA 12 (Aesno,sold by Arkema), PA 10.10 (sold by Arkema: Hiprolon 200) and PA 10.12(sold by Arkema: Hiprolon 400).

The copper-based heat stabilizer is PolyAdd P201 from Polyad Services(iodine 201).

The carbodiimide used is Stabilizer® 9000(poly(1,3,5-triisopropylphenylene-2,4-carbodiimide), sold by Raschig, orTCC, sold by Teijin.

The catalyst used is H₃PO₃ or H₃PO₄.

Anox® NDB TL89: organic stabilizer of phenol phosphite type, sold byChemtura.BBSA: n-butylbenzenesulfonamide, sold by Proviron.EPR 1801: polyolefin (maleic anhydride-functionalized ethylenecopolymer), sold by Exxon.Fusabond® 493: polyolefin (anhydride-functionalized ethylene copolymer),sold by DuPont.

Example 1: Determination of the Melt Viscosity of Polyamides of theInvention with or without Catalyst in the Presence or not of aCopper-Based Stabilizer and/or of a Carbodiimide

The tests (mixture of PA with or without catalyst, to which acopper-based stabilizer and/or a carbodiimide are or are not added) arecarried out on an Xplore MC15 micro compounder equipped with 111 and 123screws (screw profile 2).

The flat temperature profile at 270° C. is programmed.

The various mixtures are produced with a screw speed of 100 rpm and arecirculation time of 25 minutes, to which the machine feed time, i.e.between 1′30 and 2′, has to be added.

The tests are carried out while flushing with nitrogen (0.5 bar).

The normal force is measured in N. It represents the change in the meltviscosity.

The viscosity at T0 and its change at T+30 minutes are determined byplate-plate oscillatory rheology.

Plate-plate: 30 min at 270° C. 10 rad/sec 5% deformation according tothe following operatingconditions:

Appliance: Physica MCR301

Geometry: parallel plates with a diameter of 25 mm

Temperatures: 270° C.

Frequency: 10 rad·s⁻¹Duration: 30 minutesAtmosphere: Flushing with nitrogen.

Shearing of 10 s⁻¹

Example 1.1: PA 11, PA 12 and PA 10.10 without Catalyst: With or withoutCopper-Based Heat Stabilizer and/or Carbodiimide

The percentages are shown by weight.

The melt viscosity is determined at T0 and after 30 minutes.

The inherent viscosity is determined in m-cresol according to thestandard ISO 307-2007.

The method is well known to a person skilled in the art. The standardISO 307-2007 is followed but with the solvent being changed (use ofm-cresol instead of sulfuric acid) and the temperature being 20° C.

PA 11 PA 11 PA 11 Inherent viscosity 1.45 1.45 1.45 Catalyst — — —Copper-based heat — 0.25% iodine 201 0.25% iodine 201 stabilizerCarbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. Pa · s Pa · s Pa· s 10 rad/sec (melt viscosity) T0 384 No RIV 5350 After 30 min 807 NoRIV 5278 Comment Too fluid Too fluid Too fluid “No RIV” means that thereis no rise in viscosity.

A PA 11, without catalyst, with a relatively high inherent viscosity(1.45, extrusion grade), is not viscous enough, whether withcopper-based stabilizer alone or copper-based stabilizer andcarbodiimide.

The addition of 0.25% of iodine 201 does not increase the viscosity.

The addition of carbodiimide provides a rise in melt viscosity which,however, is not sufficient for the transformation of the product.

PA 12 PA 12 Inherent viscosity 1.60 1.60 Catalyst — — Copper-based heat— 0.25% iodine 201 stabilizer Carbodiimide — 1% Stabilizer 9000Plate-plate 270° C. 10 Pa · s Pa .s rad/sec (melt viscosity) T0 71529000 After 30 min 7800 10000 Comment Too fluid Too fluid

A PA 12 (Aesno from Arkema without chain-limiting agent), withoutcatalyst, with a high inherent viscosity (1.6), is not viscous enougheven with addition of copper-based stabilizer and carbodiimide.

The addition of carbodiimide provides a rise in melt viscosity which,however, is not sufficient for the transformation of the product.

PA 10.10 PA 10.10 PA 10.10 Inherent viscosity 1.35 1.35 1.35 Catalyst —— — Copper-based heat — 0.25% iodine 201 0.25% iodine 201 stabilizerCarbodiimide — — 1% Stabilizer 9000 Plate-plate 270° C. Pa · s Pa · s Pa· s 10 rad/sec (melt viscosity) T0 1650 No RIV 7685 After 30 min 2648 NoRIV 9635 Comment Too fluid Too fluid Too fluid

A PA 10.10, with a medium inherent viscosity (1.35), is too fluid,whether with copper-based stabilizer to which carbodiimide has or hasnot been added.

Consequently, the problem of the melt inherent viscosity cannot besolved by increasing the starting inherent viscosity.

Example 1.2: PA 11, PA 10.10 and PA 10.12 with Catalyst: With or withoutCopper-Based Heat Stabilizer and/or Carbodiimide

The percentages are shown by weight.

PA 11 Catalyzed PA 11 Catalyzed PA 11 Inherent viscosity 1.45 1.45 1.45Catalyst 600 ppm H₃PO₄ 600 ppm H₃PO₄ 600 ppm H₃PO₄ Copper-based heat —0.25% iodine 0.25% iodine 201 stabilizer 201 Carbodiimide — — 1%Stabilizer Plate-plate 270° C. 9000 10 rad/sec Pa · s Pa · s Pa · s(melt viscosity) T0 13500 1550 19000 After 30 min 30000 7300 23000Comments Too much Too fluid Invention change Change after 21 000, i.e. 5% 400 sec +55% Change after 148% 22% 30 min

A PA 11 with a relatively high inherent viscosity (1.45; extrusiongrade) is sufficiently viscous in the molten state at T0 (i.e., a meltviscosity of greater than or equal to approximately 13 000 Pa·s) butchanges too much since the melt viscosity is very markedly greater than23 000 Pa·s).

The addition of a heat stabilizer to the catalyzed PA 11 does not makeit possible to improve the viscosity, quite the opposite since thelatter falls drastically, stopping even the rotation.

On the other hand, the addition of a heat stabilizer and carbodiimidemakes it possible not only to obtain a melt viscosity of greater than orequal to approximately 13 000 Pa·s but a melt viscosity which is alsostable for at least 30 minutes.

PA 10.10 PA 10.10 PA 10.10 Inherent viscosity 1.45 1.45 1.45 Catalyst2000 ppm 2000 pm 2000 ppm H₃PO₄ H₃PO₄ H₃PO₄ Copper-based heat — 0.2%iodine 201 0.2% iodine 201 stabilizer Carbodiimide — — 1% Stabilizer9000 Plate-plate 270° C. Pa · s Pa · s Pa · s 10 rad/sec (meltviscosity) T0 9369 10200 13357 After 30 min 12805 16400 20313 CommentToo fluid Too fluid Invention Change after 30 min 52%

A PA 10.10 with an inherent viscosity of 1.45 comprising only a catalystis not sufficiently viscous in the molten state at T0 (i.e., a meltviscosity of less than 13 000 Pa·s).

The addition of a heat stabilizer does not make it possible to achieve asufficient melt viscosity.

On the other hand, the addition of a heat stabilizer and carbodiimidemakes it possible not only to obtain a melt viscosity of greater than orequal to approximately 13 000 Pa·s but a melt viscosity which is alsostable for at least 30 minutes.

PA 10.12 PA 10.12 PA 10.12 Inherent viscosity 1.4 1.4 1.4 Catalyst 100ppm 100 ppm 100 ppm H₃PO₄ H₃PO₄ H₃PO₄ Copper-based heat — 0.2% iodine201 0.2% iodine 201 stabilizer Carbodiimide — — 1% Stabilizer 9000Plate-plate 270° C. Pa · s Pa · s Pa · s 10 rad/sec (melt viscosity) T06156 9000 17653 After 30 min 27558 17000 19772 Comment Too fluid Toofluid Invention and too and too much change much change Change after 30min 347% 89% 12%

In the same way, with a PA 10.12 with an inherent viscosity of 1.4comprising only a catalyst, the melt viscosity at T0 is too low (lessthan 13 000 Pa·s).

The addition of a heat stabilizer does not make it possible to achieve asufficient melt viscosity.

On the other hand, the addition of a heat stabilizer and carbodiimidemakes it possible not only to obtain a melt viscosity of greater than orequal to approximately 13 000 Pa·s but a melt viscosity which is alsostable for at least 30 minutes.

Example 2: Influence of the Presence of Catalyst and of the Proportionof a Copper-Based Stabilizer and/or Carbodiimide on the RheologicalProperties of the Polyamides of the Invention Example 2.1

The percentages are shown by weight.

The polyamide used for all the tests of this example is PA 11 with aninherent viscosity of 1.45 as above.

Copper-based heat stabilizer Catalyst (Iodine 201) % CarbodiimideViscosity (ppm) by weight % by weight Rheology stability 0 0 0 − ++ 0 01 − ++ 0 0 1.5 + + 0 0 2 + + 600 0 0 + − 600 0 1 − − 600 0.25 0 − + 6000.25 1 ++ ++The remainder to 100% is, in each case, the percentage by weight of PA11.

“−” means that the value obtained is insufficient for the transformation

“+” means that the value is borderline for the transformation

“++” means that the value obtained is comfortable for the transformation

This example shows that the most important aspect for the transformationis not the inherent viscosity value but the value of the melt viscositywith the catalyst/copper-based heat stabilizer/carbodiimide combination.

Example 2.2: The Polyamide Used for all the Tests of this Example is PA11

The percentages shown are by weight.

Inherent viscosity Plate-plate at T0 PA 11 + 600 ppm H₃PO₄ 1.77 15000Noncatalyzed PA 11 + 1% 1.80  6600 Stabilizer ® 9000 Noncatalyzed PA11 + 2.25 12130 1.5% Stabilizer ® 9000 PA 11 + 600 ppm H₃PO₄ + 2.3020000 1% Stabilizer ® 9000 + 0.25% iodine 201

There is no correlation between the viscosity in solution (inherentviscosity in meta-cresol) and the melt viscosity. This can be explainedby the polydispersity index representative of the branchings.

Example 3: Evaluation of the Compositions of the Invention AdditionallyComprising Polyolefins and/or Plasticizers and/or Additives: ThermalBehavior at 140° C.

The proportions shown are percentages by weight, with respect to thetotal weight of the composition.

Test on twin-screw at 280° C. —300 rev/min under vacuum—600 mmHg (Werner40) at 60 kg/h.

The PA base is dried (moisture content<0.1%).

Comp. 1 Comp. 2 Comp. 3 Comp. 4 Inv. 1 Inv. 2 Anox NDB TL89 1.2 BBSA 6 610 6 6 6 PA 11 + 600 ppm 82.8 83.8 82.8 83.3 H₃PO₄ Inherent viscosity1.45 EPR 1801 10 10 10 10 Fusabond 493 10 6 iodine 201 0.2 0.2 0.2 0.20.2 PA 11 inherent 82.5 82.5 viscosity 1.45 Stabilizer 9000 0 1.3 1.3 01 TCC 0.5 Head pressure 23 35 33 16.5 40 40 (bar) Torque (%) 71 68 63 6386 82 RCG at 260° C. 5 min 2819 2209 1936 3830 at 100 sec⁻¹: in Pa.splate-plate at 10 13000 10300 9800 1200 14000 13000 rad/sec: T0 at 270°C. in Pa.s plate-plate at 10 31800 5140 2770 8000 21000 19000 rad/sec:after 30 min at 270° C. in Pa.s Test specimens 720 h >2000 h >2000h >2000 h ISO 527-2 1BA Half life at 140° C. Corrected inherent 1.722.22 2.49 1.50 2.31 2.2 viscosity

The half life measured with regard to the elongation at break changesfrom 30 days for the comparative composition 1 (PA 11+600 ppm ofcatalyst), which does not comprise heat stabilizer and carbodiimide, to90 days for a composition of the invention simultaneously comprising acatalyst (same proportion as the comparative composition 1), acopper-based stabilizer and a carbodiimide.

The composition according to the invention is more viscous than thecomparative composition 4, the only difference being the presence ofcarbodiimide in the formulation according to the invention (at T0 andT=30 min).

Furthermore, the comparative composition 1 exhibits a melt viscositywhich a priori seems good (T0=13 000) but which changes much too much upto T=30 min, thus not making it difficult to transform it, in contrastto the composition according to the invention.

Moreover, the comparative compositions 2 and 3, which do not comprisecatalyst but comprise a carbodiimide in a greater proportion than thatof the composition of the invention (1.3% instead of 1%), not only havemelt viscosities at T=0 which do not reach the required value of 13 000Pa·s but also are completely devoid of stability since the viscosity atT=30 min strongly decreases.

Example 4: Resistance to Hydrolysis of a Formulation of the Invention(Example 3) Compared with that of a Besno P40 TL

Besno Example 3 of P40 TL the invention Thermal stability at 140° C. 700h 2000 h Half life Resistance to hydrolysis 280 h  950 h 140° C. Volvicwater pH 4 Time in order to have 50% absolute of elongation at breakPlate-plate viscosity at 270° C. 10 rad/sec, 5% deformation T0  900014000 T = 30 min 32000 21000

The Besno P40 TL product is an Arkema Offshore referencePA11+H₃PO₄+plasticizer+heat stabilizer.

This table shows that the compounds of the invention exhibit a stabilityto hydrolysis and a melt viscosity which is improved, whatever the time(T=0 or T=30 min).

Example 5: Comparison of the Properties of the Compositions According tothe Invention with the Comparative Compositions

Carb. Stab. High Stable Cat. % by % by vis- vis- PA (ppm) weight weightcosity cosity Hyd. Ox. PA 11 0 0 0 − ++ − − PA 11 0 1 0 + ++ + − PA 11 00 0.2 − ++ + ++ PA 11 0 1 0.2 + ++ ++ ++ PA 11 600 0 0 ++ − − − PA 11600 0 0.2 − ++ + ++ PA 11 600 1 0 − − + − PA 11 600 1 0.2 ++ ++ ++ ++ PA11: Inherent viscosity 1.45. Cat.: H₃PO₄ catalyst. Carb.:polycarbodiimide Stabilizer 9000. Stab.: Copper-based heat stabilizer(Iodine 201). Hyd.: Resistance to hydrolysis. Ox.: Resistance tooxidation. − means that the value obtained is insufficient for thedesired property with regard to the service performances. + means thatthe value obtained is borderline for the desired property with regard tothe service performances. ++ means that the value obtained iscomfortable for the desired property with regard to the serviceperformances. Only the composition simultaneously comprising a catalyst,a polycarbodiimide and a heat stabilizer makes it possible to obtain agood value for the six properties desired with regard to the serviceperformances.

EMBODIMENTS

1. The use of at least one catalyst, of at least one copper-based heatstabilizer and of at least one oligo- or polycarbodiimide with a matrixcomprising at least one polyamide, in order to form a composition whichexhibits a good melt viscosity and which is stable in transformation,especially in extrusion.2. The use as in embodiment 1, characterized in that said melt viscosityof said composition is substantially constant between 1 minute and atleast 5 minutes, especially between 1 minute and 5 minutes.3. The use as in embodiment 1 or 2, characterized in that saidcomposition additionally exhibits a resistance to thermal oxidation.4. The use as in one of embodiments 1 to 3, characterized in that saidcomposition exhibits a melt viscosity of approximately 13 000 toapproximately 23 000 Pa·s, as determined by oscillatory rheology at 270°C. at 10 rad/sec while flushing with nitrogen with 5% deformation andshearing of 10 sec⁻¹ between two parallel plates with a diameter of 25mm.5. The use as in embodiment 4, characterized in that said melt viscosityis comprised of approximately 13 000 to approximately 23 000 Pa·s for atleast 30 minutes, as determined by oscillatory rheology at 270° C. at 10rad/sec while flushing with nitrogen with 5% deformation and shearing of10 sec⁻¹ between two parallel plates with a diameter of 25 mm.6. The use as in one of embodiments 1 to 5, characterized in that theproportion by weight of catalyst is comprised of approximately 50 ppm toapproximately 5000 ppm, especially of approximately 100 to approximately3000 ppm, with respect to the total weight of the composition.7. The use as in one of embodiments 1 to 6, characterized in that thecatalyst is chosen from phosphoric acid (H₃PO₄), phosphorous acid(H₃PO₃), hypophosphorous acid (H₃PO₂) or a mixture of these.8. The use as in one of embodiments 1 to 7, characterized in that theproportion by weight of copper-based heat stabilizer com is comprised ofapproximately 0.05% to approximately 1%, especially of approximately0.05% to approximately 0.3%, with respect to the total weight of thecomposition.9. The use as in embodiment 8, characterized in that the copper-basedheat stabilizer is a mixture of potassium iodide and copper iodide.10. The use as in one of embodiments 1 to 9, characterized in that theproportion by weight of oligo- or polycarbodiimide is comprised ofapproximately 0.1 to approximately 3%, especially of 0.5 to 2%, and inparticular approximately equal to 1%, with respect to the total weightof the composition.11. The use as in embodiment 10, characterized in that the oligo- orpolycarbodiimide is chosen from a Stabilizer, especially Stabilizer®9000, a Stabaxol®, in particular a Stabaxol® P, especially Stabaxol®P100 or Stabaxol® P400, or a mixture of these.12. The use as in one of embodiments 1 to 11, characterized in that thethermoplastic polymer is a polyamide chosen from an aliphatic polyamide,a cycloaliphatic polyamide, an aromatic polyamide or a mixture of these.13. The use as in embodiment 12, characterized in that the polyamideexhibits a M.p. comprised of 160° C. to 290° C., determined according tothe standard ISO 11357-3 (2013).14. The use as in embodiment 12 or 13, characterized in that thepolyamide is chosen from: PA 11, PA 12, 11/10.T, PA 10.10, PA 10.12 andthe copolyamides 11/12 having either more than 90% of units 11 or morethan 90% of units 12.15. A viscous composition which is stable in transformation as definedin embodiment 1, characterized in that it comprises, with respect to thetotal weight of the composition: a. 20.5 to 99.845% by weight of atleast one polyamide as defined in one of embodiments 12 to 14;

-   -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 0 to 15% of at least plasticizer;    -   f. 0 to 30% of at least one polyolefin;    -   g. 0 to 30% of at least one additive.        16. The composition as in embodiment 15, characterized in that        it consists of:    -   a. 64.5 to 98.745% by weight of at least one polyamide as        defined in one of embodiments 12 to 14;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 30% of at least one polyolefin;    -   f. 0.1 to 1% of at least one additive.        17. The composition as in embodiment 15, characterized in that        it consists of:    -   a. 49.50 to 97.745% by weight of at least one polyamide as        defined in one of embodiments 12 to 14;    -   b. 0.005 to 0.5% by weight of at least one catalyst;    -   c. 0.05 to 1% by weight of at least one copper-based heat        stabilizer;    -   d. 0.1 to 3% by weight of at least one oligo- or        polycarbodiimide;    -   e. 1 to 15% of at least plasticizer;    -   f. 1 to 30% of at least one polyolefin;    -   g. 0.1 to 1% of at least one additive.        18. The composition as in one of embodiments 15 to 17,        characterized in that the polyamide is chosen from an aliphatic        polyamide, a cycloaliphatic polyamide, an aromatic polyamide or        a mixture of these.        19. The composition as in one of embodiments 15 to 18,        characterized in that the polyamide exhibits a M.p. comprised of        160° C. to 290° C., determined according to the standard ISO        11357-3 (2013).        20. The composition as in one of embodiments 15 to 19,        characterized in that the polyamide is chosen from: PA 11, PA        12, 11/10.T, PA 10.10, PA 10.12 and the copolyamides 11/12        having either more than 90% of units 11 or more than 90% of        units 12.        21. The composition as in one of embodiments 15 to 20,        characterized in that the catalyst is chosen from phosphoric        acid (H₃PO₄), phosphorous acid (H₃PO₃), hypophosphorous acid        (H₃PO₂) or a mixture of these.        22. The composition as in one of embodiments 15 to 21,        characterized in that the copper-based heat stabilizer is a        mixture of potassium iodide and copper iodide.        23. The composition as in one of embodiments 15 to 22,        characterized in that the oligo- or polycarbodiimide is chosen        from a Stabilizer, especially Stabilizer® 9000, a Stabaxol®, in        particular a Stabaxol® P, especially Stabaxol® P100 or Stabaxol®        P400, or a mixture of these.        24. The use of a composition as defined in one of embodiments 15        to 23 for forming a structure, such as:

a flexible pipe intended for the transportation of gas or for theexploitation of offshore oil deposits,

a flexible pipe for motor vehicles, in particular for the transportationof fuel (gasoline, diesel, biodiesel or ethanol), for refrigeration, forair conditioning or for ducts produced in particular by extrusion-blowmolding for supplying with air,

a hollow body, a molding or a sports item.

25. The use as in embodiment 24, characterized in that the a flexiblepipe intended for the transportation of gas or for the exploitation ofoffshore oil deposits exhibits a good resistance to thermal oxidationand a resistance to hydrolysis.26. The use as in embodiment 24 or 25, characterized in that the pipeexhibits a working temperature of at least 70° C. for 20 years.27. The use as in one of embodiments 24 to 26, characterized in that thecomposition is as defined in one of embodiments 16 and 18 to 23 and thestructure is a pipe is intended for the transportation of gas.28. The use as in one of embodiments 24 to 27, characterized in that thecomposition is as defined in one of embodiments 17 to 23 and thestructure is a flexible pipe intended for the exploitation of offshoreoil deposits.29. The use as in one of embodiments 24 to 27, characterized in that thecomposition is as defined in one of embodiments 17 to 23 and thestructure is a flexible pipe for motor vehicles, in particular for thetransportation of fuel (gasoline, diesel, biodiesel or ethanol), forrefrigeration, for air conditioning or for ducts produced in particularby extrusion-blow molding for supplying with air.30. A flexible pipe intended for the transportation of gas or for theexploitation of offshore oil deposits, or for motor vehicles, inparticular for the transportation of fuel (gasoline, diesel, biodieselor ethanol), for refrigeration, for air conditioning or for supplyingwith air, as defined in embodiment 24, comprising at least one layer ofa composition as defined in one of embodiments 15 to 23.31. The flexible pipe as in embodiment 30, characterized in that saidlayer is the layer in contact with the fluid and the composition is asdefined in one of embodiments 16 and 18 to 23, intended for thetransportation of gas.32. The flexible pipe as in embodiment 31, characterized in that it canadditionally comprise at least one second layer, in particular made ofthermoplastic.33. The flexible pipe as in embodiment 30, characterized in that saidlayer is the internal layer of a flexible pipe intended for theexploitation of offshore oil deposits and the composition is as definedin one of embodiments 17 to 23.34. The pipe as in embodiment 30, characterized in that said layer isthe external layer of a flexible pipe intended for the exploitation ofoffshore oil deposits and the composition is as defined in one ofembodiments 17 to 23.35. The pipe as in embodiment 30, characterized in that it comprises aninternal layer and an external layer which consist of a composition asdefined in one of embodiments 17 to 23, said internal and externallayers consisting of the same composition of the invention or eachconsisting of a different composition of the invention.

1. A viscous composition which is stable in transformation, thecomposition formed from at least one catalyst, of at least onecopper-based heat stabilizer and of at least one oligo- orpolycarbodiimide with a matrix comprising at least one polyamide,wherein the composition comprises, with respect to the total weight ofthe composition: a. 20.5 to 99.845% by weight of at least one polyamide;b. 0.005 to 0.5% by weight of at least one catalyst; c. 0.05 to 1% byweight of at least one copper-based heat stabilizer; d. 0.1 to 3% byweight of at least one oligo- or polycarbodiimide; e. 0 to 15% of atleast plasticizer; f. 0 to 30% of at least one polyolefin; g. 0 to 30%of at least one additive.
 2. The composition as claimed in claim 1,wherein the composition consists of: a. 64.5 to 98.745% by weight of theat least one polyamide; b. 0.005 to 0.5% by weight of at least onecatalyst; c. 0.05 to 1% by weight of at least one copper-based heatstabilizer; d. 0.1 to 3% by weight of at least one oligo- orpolycarbodiimide; e. 1 to 30% of at least one polyolefin; f. 0.1 to 1%of at least one additive.
 3. The composition as claimed in claim 1,wherein the composition consists of: a. 49.50 to 97.745% by weight ofthe at least one polyamide; b. 0.005 to 0.5% by weight of at least onecatalyst; c. 0.05 to 1% by weight of at least one copper-based heatstabilizer; d. 0.1 to 3% by weight of at least one oligo- orpolycarbodiimide; e. 1 to 15% of at least plasticizer; f. 1 to 30% of atleast one polyolefin; g. 0.1 to 1% of at least one additive.
 4. Thecomposition as claimed in claim 1, wherein the polyamide is chosen froman aliphatic polyamide, a cycloaliphatic polyamide, an aromaticpolyamide or a mixture of these.
 5. The composition as claimed in claim1, wherein the polyamide exhibits a M.P. comprised of 160° C. to 290°C., determined according to the standard ISO 11357-3 (2013).
 6. Thecomposition as claimed in claim 1, wherein the polyamide is chosen from:PA 11, PA 12, 11/10.T, PA 10.10, PA 10.12 and the copolyamides 11/12having either more than 90% of units 11 or more than 90% of units
 12. 7.The composition as claimed in claim 1, wherein the catalyst is chosenfrom phosphoric acid (H₃PO₄), phosphorous acid (H₃PO₃), hypophosphorousacid (H₃PO₂) or a mixture of these.
 8. The composition as claimed inclaim 1, wherein the copper-based heat stabilizer is a mixture ofpotassium iodide and copper iodide.
 9. The composition as claimed inclaim 1, wherein the oligo- or polycarbodiimide is chosen from aStabilizer, a Stabaxol®, or a mixture of these.
 10. A structurecomprising the composition as defined in claim 1, wherein structure isselected from: a flexible pipe configured for the transportation of gasor for the exploitation of offshore oil deposits, a flexible pipe formotor vehicles, a hollow body, a molding or a sports item.
 11. Thestructure as claimed in claim 10, wherein the structure is a flexiblepipe configured for the transportation of gas or for the exploitation ofoffshore oil deposits, wherein the structure exhibits a good resistanceto thermal oxidation and a resistance to hydrolysis.
 12. The structureas claimed in claim 10, wherein the structure is a flexible pipeconfigured for the transportation of gas or for the exploitation ofoffshore oil deposits, wherein the flexible pipe exhibits a workingtemperature of at least 70° C. for 20 years.
 13. The structure asclaimed in claim 10, wherein the composition consists of: a. 64.5 to98.745% by weight of the at least one polyamide; b. 0.005 to 0.5% byweight of at least one catalyst; c. 0.05 to 1% by weight of at least onecopper-based heat stabilizer; d. 0.1 to 3% by weight of at least oneoligo- or polycarbodiimide; e. 1 to 30% of at least one polyolefin; f.0.1 to 1% of at least one additive, and wherein the structure is a pipeis configured for the transportation of gas.
 14. The structure asclaimed in claim 10, wherein the composition consists of: a. 49.50 to97.745% by weight of the at least one polyamide; b. 0.005 to 0.5% byweight of at least one catalyst; c. 0.05 to 1% by weight of at least onecopper-based heat stabilizer; d. 0.1 to 3% by weight of at least oneoligo- or polycarbodiimide; e. 1 to 15% of at least plasticizer; f. 1 to30% of at least one polyolefin; g. 0.1 to 1% of at least one additive,and wherein the structure is a flexible pipe configured for theexploitation of offshore oil deposits.
 15. The structure as claimed inclaim 10, wherein the composition consists of: a. 49.50 to 97.745% byweight of the at least one polyamide; b. 0.005 to 0.5% by weight of atleast one catalyst; c. 0.05 to 1% by weight of at least one copper-basedheat stabilizer; d. 0.1 to 3% by weight of at least one oligo- orpolycarbodiimide; e. 1 to 15% of at least plasticizer; f. 1 to 30% of atleast one polyolefin; g. 0.1 to 1% of at least one additive, and whereinthe structure is a flexible pipe for motor vehicles.
 16. A flexible pipeconfigured for the transportation of gas or for the exploitation ofoffshore oil deposits, or for motor vehicles, in particular for thetransportation of fuel (gasoline, diesel, biodiesel or ethanol), forrefrigeration, for air conditioning or for supplying with air, theflexible pipe comprising at least one layer of a composition as definedin claim
 1. 17. The flexible pipe as claimed in claim 16, wherein saidlayer is the layer in contact with the fluid and configured for thetransportation of gas, wherein the composition consists of: a. 64.5 to98.745% by weight of the at least one polyamide; b. 0.005 to 0.5% byweight of at least one catalyst; c. 0.05 to 1% by weight of at least onecopper-based heat stabilizer; d. 0.1 to 3% by weight of at least oneoligo- or polycarbodiimide; e. 1 to 30% of at least one polyolefin; f.0.1 to 1% of at least one additive.
 18. The flexible pipe as claimed inclaim 17, wherein the flexible pipe comprises at least one second layermade of thermoplastic.
 19. The flexible pipe as claimed in claim 16,wherein said layer is the internal layer of a flexible pipe configuredfor the exploitation of offshore oil deposits and wherein thecomposition consists of: a. 49.50 to 97.745% by weight of the at leastone polyamide; b. 0.005 to 0.5% by weight of at least one catalyst; c.0.05 to 1% by weight of at least one copper-based heat stabilizer; d.0.1 to 3% by weight of at least one oligo- or polycarbodiimide; e. 1 to15% of at least plasticizer; f. 1 to 30% of at least one polyolefin; g.0.1 to 1% of at least one additive.
 20. The flexible pipe as claimed inclaim 16, wherein said layer is the external layer of a flexible pipeconfigured for the exploitation of offshore oil deposits and wherein thecomposition consists of: a. 49.50 to 97.745% by weight of the at leastone polyamide; b. 0.005 to 0.5% by weight of at least one catalyst; c.0.05 to 1% by weight of at least one copper-based heat stabilizer; d.0.1 to 3% by weight of at least one oligo- or polycarbodiimide; e. 1 to15% of at least plasticizer; f. 1 to 30% of at least one polyolefin; g.0.1 to 1% of at least one additive.
 21. The flexible pipe as claimed inclaim 16, wherein the pipe comprises an internal layer and an externallayer, each of which consist of a composition wherein the compositionconsists of: a. 49.50 to 97.745% by weight of the at least onepolyamide; b. 0.005 to 0.5% by weight of at least one catalyst; c. 0.05to 1% by weight of at least one copper-based heat stabilizer; d. 0.1 to3% by weight of at least one oligo- or polycarbodiimide; e. 1 to 15% ofat least plasticizer; f. 1 to 30% of at least one polyolefin; g. 0.1 to1% of at least one additive.